1. Field of the Invention
The present invention relates to a spindle motor for use in a disk drive apparatus.
2. Description of the Related Art
Spindle motors arranged to rotate disks about central axes thereof are typically installed in electronic devices, such as hard disk apparatuses and optical disk apparatuses. Such spindle motors include a stationary portion fixed to a housing of the electronic device, and a rotating portion arranged to rotate while supporting the disk(s).
Some known motors used in disk drive apparatuses also include a bearing mechanism using fluid dynamic pressure. A spindle motor disclosed in JP-A 2009-136143 includes a fixed shaft, an annular bearing component, a rotor component, and an annular cover. The bearing component is arranged at an upper end portion of the fixed shaft. The bearing component is defined integrally with the fixed shaft. The rotor component is arranged outside the fixed shaft. The annular cover is arranged above the bearing component. A radially outer end portion of the annular cover is adhered to an upper end portion of the rotor component. An outer circumferential surface of the bearing component is arranged opposite to an inner circumferential surface of the upper end portion of the rotor component. A seal gap is defined between the outer circumferential surface of the bearing component and the inner circumferential surface of the upper end portion of the rotor component. The seal gap is covered with the annular cover.
As described in JP-A 2009-136143, in some motors, a cap member arranged to cover a capillary seal gap is arranged in a rotating portion. In such a motor, the annular cover is arranged to define a labyrinth seal together with an end portion of the shaft, and this reduces exchange of air and accompanying evaporation of a bearing fluid. For example, in a small-sized and high-performance electronic device, such as a notebook PC in which a disk drive apparatus is installed, a CPU and the like inside a case thereof generate a large amount of heat. If the heat generated in the CPU and the like is transmitted to the rotating portion of the motor, the heat may cause a deformation and a warping of the rotating portion. If this happens, the motor is unable to rotate stably. Accordingly, there is a demand for a motor structure with which a motor is unlikely to be deformed even when the motor is exposed to heat from a heat source, such as the CPU.